1. Field of the Invention
This invention generally relates to heat resistant fabrics and yarn for making the same. More specifically, this invention relates to a heat resistent cost effective yarn and fabrics made therefrom which are suitable for use as primary clothing in heavy molten metal splash applications.
2. Prior Art
It has heretofore been common practice to make heat resistant fabrics from yarns of asbestos fibers or synthetic fibers that have high heat resistance. The high heat resistant asbestos fiber offered one of the highest level of resistance to molten metal splashes, however, the use of asbestos fibers has been considered hazardous to the user as well as other persons exposed to the fibers. As a result, synthetic fibers have found increasing use. The asbestos substitute fabrics are suitable for some molten metal splash applications. However, these prior synthetic attempts did not offer the thermal protection or the cost effectiveness of the present invention.
In the metals industry, workers are routinely exposed to heavy molten metal splashes. It is a common practice to wear flame resistant (FR) primary garments for protection. Generally, the primary garments are worn over secondary garments, such as typical work clothing. Primary garments are heavy fabric and sometimes laminated with an aluminum film on one side.
In the aluminum industry, the primary garments are made from FR treated wool, FR cotton and PVA fibers. Since molten aluminum does not radiate a large amount of heat, these garments are not generally laminated. The fabric weight varies between 10 to 20 oz/yd.sup.2. In addition to the above, a variety of high heat and flame resistant synthetic fibers such as aramids, PBI, PAN based carbon and phenolic fibers have been tried individually and in various combinations. Due to the nature of molten aluminum--mainly its ductility and high temperature--these products have failed to meet the industry's requirements. The temperature of molten aluminum is approximately 1400.degree.-1500.degree. F. When molten aluminum is splashed onto primary garment fabric, it has a tendency to rapidly solidify on the fabric surface. Therefore, it is imperative that the surface of the primary garment provide thermal protection. FR treated wool, FR cotton and PVA fibers offer the required properties. Although, fibers like PBI, aramids and phenolic are high heat and flame resistant fibers that offer high limiting oxygen index (LOI) values from 40-30 LOI, fabrics made from these fibers (either individually or in combination), do not offer the desired thermal protection against molten aluminum splashes. The reason being the fiber's inability to take spontaneous thermal shocks arising from the impact of molten aluminum. For example, molten aluminum sticks to the aramid fabric thus resulting into a much higher heat transfer through the fabric. Aramid fabrics are widely used for fire fighters' turnout coats for open-flame exposure, however, the same type of fabric fails in a molten aluminum splash application.
Similarly, in the steel industry, which has the hazard of heavy molten steel (molten iron is generally in the temperature range of 2700.degree.-3000.degree. F.) splash, the substrate fabrics for the primary garments are made from fibers such as PAN based carbon, Kevlar and FR wool. Generally, these steel industry fabrics are laminated with an aluminum film. The aluminum film provides heat reflectivity qualities which are considered essential for protecting the wearer from the heavy doses of radiant heat emitting from molten steel and high temperature furnaces used in the manufacture of steel. The thermal impact of a molten iron splash requires the substrate fabrics to provide a significant amount of thermal protection. For example, 14 to 19 oz/yd.sup.2 substrate fabrics laminated with aluminum film (on one side) and made from FR cotton, FR acrylic, FR rayon, Nomex and PBI fibers (either alone or blended), exhibit very poor performance against heavy molten iron splashes. In fact, some of these fabrics permit heat transfer that can cause second and third degree burns, and, in spite of being flame resistant fabrics, may ignite upon spontaneous impact of the molten iron. On the other hand, substrate fabrics of similar weight made from FR wool, PAN based carbon and/or Kevlar.RTM., provide better protection against minor molten iron splash. However, with a major molten iron splash, these later fabrics offer very limited or no protection.
As can be seen from the above, the art desires a yarn and fabrics which are usable in heavy molten metal splash applications at a cost effective level.
The fabric of the invention employs known techniques of manufacturing a core-spun yarn with a novel fiber mix and distribution of fibers as a means to optimize cost and performance in heavy molten metal splash applications.
It is the principal object of the invention to provide a fabric for primary protective clothing which is cost effective, resistant to high temperatures, thermal shocks and suitable for application against heavy molten metal splashes.
Other objects and advantageous features of the invention will be apparent from the description and claims.